It is nearly 108 years since on 12 December 1901 Marchese Guglielmo Marconi made his pioneering trans-Atlantic transmissions and you would think that in that time everything that could be done with radio waves had been, but on course it is not so. Man's ingenuity know no bounds and advances continue for the uses of radio, in all sorts of fields, that Marconi would never have imagined.
Ground penetrating Radar has been around in some form or other for years now and is used to detect underground cables and pipes. It has always been limited to a fairly low penetration depth of a few of metres and what was needed was to use low frequencies to get deeper. The problem with using LF is you need BIG antennas which makes the equipment bulky to say the least. Researchers have now mounted their Marconi on trailers and by careful choice of frequencies which avoid interference from things like radio stations and using ultra sensitive receivers they can map, in 3D, a fairly large area with just a few relocations of the mast.
So why you ask are they doing this? Well, you might think it was to detect hidden mine shafts or to find fissures in the Earths crust to detect seismic activity but no, it is all designed to detect smugglers on the US/Mexican border. I am sure it will have other uses but this is where the funding for this research comes from keeping Mexicans and drugs out of the US. The researchers are confident that their more sensitive mobile radar system will soon be detecting tunnels that had previously been missed. Criminal underground beware.